1. Field of the Invention
The present invention relates to recombinant RNA virus templates derived from and applicable to negative strand naturally non-segmented viruses, including the families Bornaviridae, Filoviridae, and Paramyxoviridae, and methods for generating such recombinant RNA virus templates, wherein the templates are generated from two or more recombinant RNA molecules. The recombinant RNA virus templates may be used to express heterologous gene products in appropriate host cell systems and/or to construct recombinant viruses taken from that family and that express, package, and/or present the heterologous gene product. The expression products and chimeric viruses thus prepared may advantageously be used in vaccine formulations. The present invention also relates to the corresponding genetically engineered recombinant viruses which contain modifications and/or mutations that make the recombinant virus suitable for use in vaccine and therapeutic formulations, such as an attenuated phenotype or enhanced immunogenicity.
2. Description of the Related Art
A number of DNA viruses have been genetically engineered to direct the expression of heterologous proteins in host cell systems (e.g., vaccinia virus, baculovirus, etc.). Similar advances have been made with positive-strand RNA viruses (e.g., poliovirus). The expression products of these constructs, i.e., the heterologous gene product or the chimeric virus which expresses the heterologous gene product, are thought to be potentially useful in vaccine formulations (either subunit or whole virus vaccines). One drawback to the use of viruses such as vaccinia for constructing recombinant or chimeric viruses for use in vaccines is the lack of variation in its major epitopes. This lack of variability in the viral strains places strict limitations on the repeated use of chimeric vaccinia, in that multiple vaccinations will generate host-resistance to the strain so that the inoculated virus cannot infect the host. Inoculation of a resistant individual with chimeric vaccinia will, therefore, not induce efficient immune stimulation.
By contrast, the negative-strand RNA viruses, would be attractive candidates for constructing chimeric viruses for use in vaccines. The negative-strand RNA viruses are desirable because the genetic variability or multiple serotypes of some negative-strand viruses, influenza, for example, allows for the construction of a repertoire of vaccine formulations which stimulate immunity without risk of developing a tolerance. Construction of infectious recombinant or chimeric negative-strand RNA particles was achieved with the influenza virus (U.S. Pat. No. 5,166,057 to Palese et al., incorporated herein by reference in its entirety). Additionally, the use of viruses which are not natural pathogens of humans, while they may be able to infect humans, is attractive because of the lack of pre-existing immunity in humans. Examples of negative-strand RNA viruses which are not natural pathogens of humans, but which can infect humans, include for example Newcastle disease virus (NDV), vesicular stomatitis virus (VSV), bovine respiratory syncytial virus (RSV) and avian pneumoviruses.